There are multiple definitions:

1. outer Helmholtz plane(English)

   • BGE, CE, ECD, EOF, ESI, EKG, FASS, GC, IEF, ITP, LIF, MALDI
   • Biochemistry
   • https://doi.org…82165-2.00241-5

2. hydroxyproline(English)

   • is present in essentially all tissues and all genetic types of collagen
   • Skeleton and bone (formation)
   • https://doi.org…73884-4.00020-3